TW201100751A - Equal-path interferometer - Google Patents

Abstract

An optical assembly for use in an interferometer is provided. The optical assembly includes first and second partially reflective surfaces positioned along an optical axis and oriented at different non-normal angles to the optical axis. The second partially reflective surface is configured to receive light transmitted through the first partially reflective surface along the optical path, transmit a portion of the received light to a test object to define measurement light for the interferometer and reflect another portion of the received light back towards the first partially reflective surface to define reference light for the interferometer. The reference light makes at least one round trip path between the second and first partially reflective surfaces.

Description

201100751 VI. Description of the Invention: [Technical Field of the Invention] The present invention relates to an equal path interferometer and related method. [Prior Art] An interferometer performs measurement of an object using an interference beam. Interferometers can be broadly classified into equal paths, where the +-beams cross an almost equal optical distance (eg, 'equal within tens of microns') and unequal paths, compared to the coherence length of visible white light, its optics The path difference is large (for example, more than 〇. and may reach several kilometers). The material (4) can be configured to operate with low coherence (wideband and/or inter-extended) light sources. The unequal path interferometer includes, for example, a Fizeau interferometer that can be used to test optical components. Equal-channel interferometers are of interest in optical testing, for example, for measuring the front and back surfaces of translucent objects, respectively. Equal path interferometers can also be used in interference microscopy. A low coherent acne lamp and a white LED can be used as the light source. For example, the interference microscopy design can be based on path balance and dispersion compensation of the Mirau, Michels〇n or Linnik interferometer. SUMMARY OF THE INVENTION Generally, in one feature, an interferometer provides nearly equal measurement and reference path lengths, the measurement path extends to the surface of the test object, the reference path extends to the surface of the reference element, and light from a low coherent light source can be used . 201100751 An application of the interferometer is to describe the contour of the selected surface of the object when Qiu Ba, ..., π buys no reaction to the surface of other objects. In this implementation, the unequal path fascia is suitable for equal path geometry: in some interferometers, the interference objective is used as a microscope (for example, a microscope with a low coherence source). k is often another feature, an interferometer is provided with a light source, a reference element ^ ^ M /, a medium interference 70 loss of 70 pieces, an interferometer beam splitter, and a reflection for over-reducing - Aperture light 'a brother', a temple object, and a camera such as a ^ ^ ^. The file passes through the partially reflective surface of the reference component to reach the interferometer and the spectrometer splits the light into this reference. Measure 1 beam. The reference beam interface and the private receiver reflect the reference surface reflection from the reference part of the reference piece's back into the interferometer ^^ '1 ^ ^ device, then reflect from the beam splitter for a long time, then pass the reference component, and finally. , + .s .av 峨 铋 铋 到达 到达 到达 到达 到达 到达 到达 到达 到达 到达. ^ ^,ar θ , first beam 攸 at least - the surface reflection of the object makes the ray back to the interferometer to cry η 丄 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与 与The bundles combine to create an interference pattern at the camera. The reference element and the beam splitter are interspersed with a double beam by the stray reflection from the different surfaces of the dry, step shy Μ ^ ^ ^ / '' cow. It is expected to be produced at the camera. Usually, in another feature, it is.弁α enemy 仏 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学 光学. The second part reflects the light of the table, and the part of the light is transmitted to the test object. The transmission of the reflective surface is first transmitted to the test object to define the interferometer. 5 201100751 Twilight and the other part of the received light is directed to the first - Defining the reference light of the interferometer, wherein the parametric and reflective surfaces are reflected back to the path of at least one of the back and forth between the reflective surfaces: the first embodiment of the optical assembly may include a line angle such that the reference light is in the second The reference light is passed through the first and second partial reflection surfaces to the optical axis normal angle before the partial reflection back to the reference light. Non-exposure contact makes it a partially reflective surface. The period is one and a half times the illegal line angle of the illegal line angle perpendicular to the first part of the reflective surface. '', the first partial reflective surface, the second partial reflective surface can be configured to join the reflection from the test object back to the second partial reflective surface = (in the measurement of the optical reference light at least - times back and forth the second and the second The test surface (below). The surface between the knife reflective surfaces = may include: a first optical element having a first partial reflection second second piece having a second partial reflection surface. - and a light-emitting element, each There may be another surface film. The anti-reflective plating, the h reflective surface may be respectively located on the outer surface of the optical element. The partially reflective surfaces may be formed at respective inner interfaces within the optical element. The reflective surface may be spaced apart from the second partially reflective surface by an imaging mode = focal depth greater than the interference pattern captured between the reference light and the measurement light. The optical component of the interferometer is positioned such that the reference filament passes through the depth of focus of the imaging module The inner glass may have another surface having an anti-reflective ore 6 201100751 mode. The first optical element may be oriented such that the first partial reflective surface faces the second optical element a second partial reflective surface, the anti-reflective coating of the I-optical element facing away from the second partially reflective surface. The distance between the first partially reflective surface and the second partially reflective surface is greater than the interference between the reference light and the measuring light The depth of focus of the patterned imaging module. The optical assembly may include: a dispersion compensator positioned between the first optical element and the second optical element to compensate for phase difference ' dispersion between the measuring light and the reference light The compensator is positioned adjacent to the third optical element and outside of the depth of focus of the imaging module. The first optical element can be oriented such that the first partially reflective surface faces away from the second partially reflective surface of the second optical element, and the first optical The anti-reflective coating of the component faces the second partially reflective surface. • The &sense assembly may further comprise: - a third partial reflective surface. The third partial reflective surface may be configured to: i) receive transmission through the first portion along the optical axis Reflecting the light of the surface; i 〇 transmitting part of the received light to the test object to determine the light; and iii) directing the other part of the received light toward the first partial reflective surface The shot is returned to define a second reference light to the interferometer, wherein the first reference light travels at least once back and forth between the second and first partially reflective surfaces. The optical assembly can further include: a collimator that receives light from the source and projects the collimated light onto the first partially reflective surface. The optical assembly can further include: a mirror that receives light from the source and projects the light onto the first partially reflective surface, the field mirror is positioned for reference after the reference light is reflected by the first partially reflective surface and the reference light is detected by the detector The light travels beyond the imaging path. 7 201100751 The 卩 反射 反射 reflective surface can have a reflectance ranging from about 1 〇 % to about 30%. The second partially reflective surface can have a reflectance ranging from about 4% to about 6%. An interferometric system can include the optical assembly described above and an interferometer base that includes a light source and a detector. The light source can be configured to produce light that is transmitted through the second blade reflective surface and received by the second partially reflective surface. The detector can be configured to receive the combined light comprising the measurement light and the reference light and provide information regarding the spatial distribution of the combined light. The interferometer base can include: an aperture stop positioned to block light from the interferometer base that contacts the first partially reflective surface along the optical axis and is reflected from the first partially reflective surface back to the interferometer base; - A base to support the test object. The base can be clamped to define an optical path length of the measurement light that is substantially equal to the optical path length of the reference light. The τ tw optical system can include a phase shifter 'to change the difference between the measuring light and the reference to the human to mechanically couple the interferometer mount 5 to the optical assembly and can be configured with a distance of " , W and the unit between the assembly and the test object to change the optical path length of the measurement light. The light source can be a broadband source to provide a source that can be a narrowband laser source. Interferometry measurement. The source can be a broadband mode laser mode with low coherence interferometry. The money can be driven by the laser threshold when the current of the laser threshold is driven in the broadband body when it is driven at a current lower than its laser-to-laser value, and when it is higher than the first-part reflection The surface can include 1 = medium operation. The surface of the ten sides. 201100751 • Usually 'in another feature', the interference method includes: along the first and second partial reflection surfaces, the first and second π knife reflection surfaces are different from each other in the optical axis (4), And transmitting light through the first partial file reflecting surface to the second partial reflecting surface in the direction of parallel light pumping. At the second partial reflective surface, the first portion of the light is transmitted to the test object to deliberately measure the light' and the second portion of the light is reflected back toward the first partially reflective surface to define the reference light. At the first partial reflective surface, the - portion of the first light is reflected toward the second partially reflective surface such that the reference first travels at least one back and forth between the second and first partially reflective surfaces. Embodiments of the interference method may include one or more of the following features. Orienting the second order and the second partially reflective surface can include directing the first and second partially reflective surfaces to different illegal line angles such that the reference light is at least prior to the second partial reflective surface reflecting the reference light along the optical axis Passing between the first and second partial reflective surfaces at a time. Orienting the first and second partially reflective surfaces can include directing the first and second partial reflective surfaces to different illegal line angles such that the reference light contacts the one of the partially reflective surfaces during normal passage therebetween. The method can include: in the second portion of the reflective surface 'in combination with the measurement light (after it is reflected from the test object back to the second partial reflective surface) and the reference light travels at least one time back and forth between the second and the first partial reflective surface Information about the spatial distribution of the combined light can then be provided. An aperture light barrier may be provided to block light reflected from the first portion 201100751: the reflective surface in a direction away from the second partially reflective surface. A test object having a reflective surface can be clamped to define an optical path length of the measurement light that is substantially equal to the length of the reference path. The difference in optical path length between the measuring light and the reference light can be changed. The distance between the optical assembly and the test object can be altered to change the optical path length of the measurement light, wherein the optical assembly includes first and second partially reflective surfaces. The method can include orienting the optical element having the first pupil reflective face to the outer surface s of the optical element such that the outer surface of the optical member having the first partially reflective surface faces the second partially reflective surface. The method can include transmitting the reference light from the first partially reflective surface to the second portion without passing through the a ° glass breaking member: the surface. The method can include positioning the second partially reflective surface at a distance from the first portion of the reflective surface that is greater than a depth of focus of the imaging module that detects the interference pattern between the measurement light and the reference light. The method may include passing the reference light through a dispersion compensator that compensates for a difference in phase between the measurement light and the reference light due to a difference in length of the optical path along which the measurement light travels and positions the dispersion compensator at Outside the depth of focus of the imaging module. The method may include: positioning a third reflective surface along the optical axis; orienting the third partially reflective surface parallel to the second partially reflective surface; and at the third partial reflective surface 'the light to be transmitted by the first partially reflective surface The three parts are dedicated to the δ-type object to define the measurement, and the fourth part of the % is oriented toward: the partial reflection surface is reflected back to define the second reference light; and on the first------the reflection surface, the fourth of the light A portion of the portion reflects toward the second partially reflective surface such that the second reference light travels at least once back and forth between the second and first partially reflective surfaces 10 201100751. Transmitting light through the first portion and aligning the car; the knife reflecting surface can include transmitting the collimated light to the reflective surface. The method can include transmitting light through the field mirror prior to transmitting the light through the first surface, and after the reference light is reflected by the fourth reflective surface, and before the detection, the + identification, and the reference are detected by the detector, % The mirror is positioned outside of the imaging path through which the reference light travels. Although it is described here as an interferometer for the ultimate work, the use of Ο 适当 to properly change the reference component, the concept of "seeing" can be generalized to measure any surface shape. h 幻衣 [Embodiment] Referring to Figure 1, the interferometer 1 of the prior art is provided for analyzing the front surface form or other features of an object. The interferometer (10) extracts (4) the surface of the test object m, and then provides a reference path for the surface of a reference element 104, wherein the reference path is measured and has approximately equal path lengths. In this example, the reference element 104 is a glass having a flat surface. Xie ^ first includes a plurality of partially reflective surfaces that are clamped along the aperture of the interferometer 1 - the vehicle 106 is tilted and tilted at an angle relative to the light such that the useful glaze 106 ^ ^. The optical axis 106 and the reference leading edge optical axis 106 are directed to a detector (for example, 昭 她, 、, ', machine 1 〇 8), and the unwanted light is not parallel to the optical axis 106 The direction χ, *曰^ breaks the guide and filters out. This allows the use of low-coherence light * / original 11 U and § π { walk 4 special -t- ^ * / β - and /, the measurement of transparent objects with a reflective surface becomes a valley. Here, the noun "氺" >丄 can extend the electromagnetic radiation in any area of the ultraviolet, visible, near-infrared 11 201100751 and infrared spectral regions. An illumination splitter 112 directs light from the source 110 through a collimator 114' which collimates the light and directs the light toward the reference element 104 and the interferometer beam splitter 116 in a direction parallel to the optical axis ι 6 . The reference element 1〇4 has a partially reflective (PR) plating film 118 on the surface facing the collimator 114, and has an anti-reflection (AR) plating film 12 on the surface facing the beam splitter 116. Since the PR coating 118 and the AR coating 1 20 are thin, the noun "pR coating 118," and "pr surface 118" will be used interchangeably, and the noun "AR coating 120,, and, 'AR surface 1 20" will be exchangeable. The spectroscope 丨丨6 has a partially reflective (pR) plating film 122 on the surface facing the spectroscopic element 104, and has an anti-reflection (AR) plating film 124 on the surface facing the test object 102. Because of the Pr plating film 122 and The AR coating 124 is very thin, and the nouns, 'ρβ coating 122, and pr surface 122' will be used interchangeably, and the terms "AR coating 1 24" and "AR surface 124" will be used interchangeably. The light of 114 passes through the PR coating 118 of the reference element 1 〇 4. As an example, the PR coating 118 reflects ι 7% of the incident light and transmits 83% of the incident light. Thus, 83% of the light passes through the reference element ι 4 ar The coating 120 is propagated to the pR coating 122 of the beam splitter 124, which in this case reflects 50% of the incident light and transmits 5% of the incident light. The reflected light forms a reference beam 126 and the transmitted light forms a measuring beam. 128. The reference beam 126 passes through the AR surface 120 of the reference element 1〇4 and Reflected partially from the PR surface 118 of the reference element 104. Thus, the PR surface 118 of the reference element 104 acts as a reference surface. The reflected reference beam 126 then returns to the pr surface 丨22 of the beam splitter ,6, at The point is partially 12 201100751 reflected into a dam, Gan tffcj Π; » it is in line with the original illumination and coextensive (and parallel to the optical axis f ^ direction, and finally after passing through the aperture stop 130 and the imaging lens 136 Arrive at the camera 1〇8.

The above examples are useful for measuring test objects having a surface reflectance ranging from 1% running. Depending on the application, the values of reflectance and transmittance may differ from those provided above. For example, the PR surface 118 of the reference element m can have a range from about m to about 3_reflectivity, and the PR surface 122 of the beam splitter 116 can have a reflectance ranging from about 4% to about 6%. In this routine, the reference beam 126 travels back and forth from the pR surface 122# of the beam splitter 116 to the reference element 1〇4 fine surface ι 8 and then back to the pR surface 122. As explained below (Fig. 8), the tilt angle of the reference element 1〇4 can be adjusted such that the reference beam 126 is at the reference beam 丨26 and the measuring beam j 28 . Thereafter, the pR surface 122 of the beam splitter 16 travels back and forth between the PR surface 118 of the reference element 1〇4 twice or more as explained below. This allows the distance between the PR surface 122 of the Echo splitter 116 to the surface of the test object 1〇2 to be increased when the field maintains an equal path length between the set beam 128 and the reference beam 126. The measuring beam 128 passes through the AR surface 124 of the beam splitter 116 to the test object 102' where the measuring beam 128 is reflected from at least one surface (e.g., the front surface 137) of the test object 1〇2 back to the interferometer beam splitter 116 where it A portion of the 'Beyond beam 12 8' is approximately coextensive with the original illumination and is in-line (and parallel to the optical axis 106) path through the remaining elements, and finally to the camera 108 where the beam 128 is referenced and referenced. The beam 丨 26 interferes. The result is a two-beam interference pattern which is useful, for example, for determining the surface profile of the test object 丄〇 2 13 201100751. In the example of FIG. 1 'the measurement beam 128 (after reflection from the surface of the test object 102) and the reference beam 126 (after traveling back and forth between the PR surfaces 122 and 118) are bonded to the pR surface (2) of the beam splitter 116 or overlapping. The overlapping beams then travel toward camera 108. , in addition to being referenced by V to the camera 胄 (the reference beam of part 〇 8 and the ray beam 128 ' ( (in other possible sources of accidental reflection) reference beam 1. 4 and interferometer spectrophotog 116 may not want to The desired reflection (such as 139). To isolate and remove the unwanted reflection 139, the reference beam 1〇4 and the interferometer beam splitter 116 are slightly turned at an angle as shown to direct the unwanted reflection 139 to Outside of the aperture aperture of the aperture stop ι3 。 Figure 1 shows an example of an unwanted first reflection 132 from the PR surface 118 of the reference element, and the unwanted portion 134 of the reference beam 126 is transmitted through the reference element 104 instead Reflected back toward the interferometer beam splitter 116. The unwanted first-reflection 132 and unwanted portions & 134 are blocked by the aperture stop 130. In the example of Figure 1, the interferometer beam splitter 116 is relative to the vertical optical axis 106. The orientation is tilted by an angle a. The reference element 1〇4 is tilted substantially at an angle equal to 2cx such that the reference beam 126 is illuminated at approximately normal incidence to the PR surface 118 of the reference element 104. Referring to Figure 2, in some embodiments To enter The unwanted reflections from the AR surface of the reference element 104 and the interferometer beam splitter 116 are suppressed in one step, and the reference element 104 and the interferometer beam splitter 6 can be made of wedge substrates 210 and 212, respectively. In this example, the wedge substrate 212 has a PR surface 218 facing the reference 201100751 element and an ar surface 2ΐ6 facing the test object 1〇2, ', the middle PR surface 218 and the AR surface 216 are not parallel. The wedge substrate 21〇 has a face alignment straightener 114 The outer surface and the 99 11 surface, the surface 220 and the AR surface 214 ′ facing the beam splitter, wherein the PR surface 22 〇艿ακ»志 οι/· is not parallel to the 表面 and AR surface 214. The orientation relative to the vertical optical axis 106, PR The surface? 1 garment is tilted by 218 and the PR surface 220 respectively to be substantially equal to the angles of α and 2α. The station field w is not through the use of the wedge substrates 21 and 212, and the non-phased 来自 from the AR surfaces 214 and 216 The reflection of the μ μ μ will be pushed in an angle relative to the measurement and ❹ Ο reference beam, and the door is set and taken back by the aperture stop 130. In the example of Figure 1, it is observed X. 丨θθ 表面 眺 眺 或 测 测 测 表面 表面The front surface 137 of 102. The interferometer 1 can also be used to view or measure the back surface 138 of the test object 102. The surface to be measured does not necessarily need to be the outer surface of the object. The internal interface in the optical (4) is viewed or measured. The interference pattern detected by the camera 108 is analyzed by, for example, a computer (not shown). The analysis of the interference pattern can provide information about, for example, the object m. Whether table Φ 137 matches or information with the desired surface porch. In the example of Figure 1, the interferometer is insensitive to the polarization of #沾, m耵 to nine. Illumination photodetector 112 reflects a portion of the light from source 110 (e.g., collimator 114, and transmits a portion of the returned light (e.g., collimator 114 to camera 108. In some embodiments, dry ^ The instrument can also be configured to use polarized light. For an offset 1 , a B v polarized illumination beam splitter is used and a four y knife wave plate is positioned between the beam splitter and the quasi-parentizer 114 to rotate 15 201100751 The polarization state of the light. The polarized illumination beam splitter will generally polarize all of the light guides w along the first direction (through the quarter-wave plate) and will generally return all polarizations along the first direction of the 荖笸-十^1 Light (via a quarter-wave plate) is transmitted to camera 1 〇 8. Referring to Figure 3, the invention of reference element 104 and interferometer beam splitter 116 has the benefit that they can be configured to be equal for reference beam 126 and measurement 28. Path length 'and an equal number of glass in both paths. For example, the thickness of the glass of reference element 1G4 can be the same as the thickness of the glass of beam splitter 116. Right side, in this example, measuring beam 128 from The surface 122 of the pp 矣 && of the illuminator 116 is advanced to the front surface 137 of the object 1 〇 2 and the path length back to the pr surface 122 is equal to the reference beam 126 traveling from the PR surface 122 to the reference element called the fine surface. 118 and returning to the path length of the PR surface 122. A change in environmental conditions such as temperature generally results in the same amount of phase change in the reference beam (3) and the sigma beam! 28. This is useful, for example, in low coherence interferometry, It is important to maintain the same path length for the measurement and reference beams. In some examples, the thickness of the reference elements #ι〇4 and the beam splitter (1) may vary, and an additional optical component may be used to partially or completely correct The phase difference caused by such a difference. If the back surface 138 of the test object 1〇2 or the surface inside the body of the test object 1()2 is measured, the distance between the test object 〇2 and the beam splitter ι 6 can be Adjusted 'so that the optical path length of the measuring beam traveling from the pR surface 122 to the surface to be measured is equal to the optical path length of the reference beam 16pR surface 122 traveling back to the pr surface 118 Note that since the refractive index of the test object of 16 201100751 I can be different from the refractive index of air, even if the optical path length of the measurement and reference beam is the same, the physical distance traveled by the measuring beam can be different from the physical distance traveled by the reference beam. In the example, reference element 210' and splitter! 212 also provide equal path lengths for the measurement and reference beams. Another benefit of the design of the present invention is its overall geometric and mechanical design with commercial Fizeau interferometers. Compatible, such as

Zyg0 CorP〇ration’ Middlefield, Connecticut

Interferometer for the Zygo GPTTM system. Referring to FIG. 4, an exemplary equal path interferometer 144 can be used for the phase shift interferometer interferometer 144 including an instrumentation host 142 and an interferometer subassembly 140. The interferometer sub-assembly 14 can be attached to the main unit 142 of the instrument or an accessory removed therefrom depending on the application. The main unit 142 includes a light source 146, an illumination beam splitter 112, a collimator 114, an aperture stop 13A, an imaging lens 136, and a camera 1 〇 8, similar to that shown in the example of FIG.光源 Light source 146 can be a laser source or a low coherent source. In some embodiments, the light source Ϊ 46 can be adjusted between the wide frequency 低 mode of the low coherence interferometry and the laser mode of the coherent interferometry. For example, light source 146 can be a field-emitting body that operates in a broadband mode when driven at a current below its laser threshold and in a laser mode when driven at a current above its laser threshold. In operation. Interferometer-under-assembly 140 includes an interferometer beam splitter 116 and a reference element 104' similar to that shown in the example of FIG. The position of the interferometer sub-assembly 14 可由 can be adjusted by a mechanical phase shifter 148 (represented by 147), which can have an accuracy of, for example, an i micron rating. The sai 移 移 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变 改变The assembly is coupled to a pedestal on the instrument mainframe 142 and is configured to vary the distance between the human and the human and the test object 102 to change the optical path length of the measuring beam 128. The sub-assembly U0 can be It is configured as a detachable accessory that can be mounted on the instrument main unit 142 through an accessory mounting plate 149. In this example, the interferometer 14 4 is compatible with illumination of any polarization. In some embodiments, 1 The hand can be dragged, and the interferometer 144 is configured to utilize the polarization first so that the measuring beam and the reference beam respectively have a specific polarization along a specific portion of the measuring path and the reference path technique. When the low coherent light source 146 is In use, the equal path interferometer 144 can measure, for example, a particular surface of a transparent object having a plurality of reflective surfaces. In low coherence interferometry, the 'interference effect is limited or localized to the case of the equal path". 5 display - Example Interference Signal 15(), which is measured as a function of the position of the object of the transparent object as measured by a _ broadband (center wavelength of 600 nm '15 mm full width). "Zero" object position phase In the case of the equal path, in this case, the vibration of the wave seal of the interference 15G is higher at a position close to zero, and is significantly reduced at a position 12 microns beyond the position of zero. & Figure 6 shows An example interferometric signal strength, i 6 〇, is measured as a function of the position of an object of a 40 μm thick fused silica object when measured with a broadband source (center wavelength of 600 nm, full width at half maximum of 15 nm). 18 201100751 The first peak 162 of the signal 16 出现 appears at zero. The second peak 164 of the interference signal 160 appears at -60 microns, which corresponds to the reflection from the back surface of the object. As can be seen from Figures 5 and 6 The pattern shows that the reflection from the surface on the test object 1 〇 2 that is farther away from the surface being measured, for example 20 μm, is satisfied for the equal path condition (ie, the measurement path and the reference path have substantially phase The contribution of the interference pattern generated at the path length will be negligible. In the example shown in Fig. I-4, the light reflected from the front surface 137 and the rear surface 138 of the test object 102 may all reach the camera 丨〇8. Assuming that the distance between the front and back surfaces is greater than 20 microns. When the interferometer! is used to measure the front surface 1 37, the light reflected from the back surface 丨 38 may not have any interference pattern detected on the camera 丄 (10). Significant contribution. Similarly, when the interferometer 1 is used to measure the back surface 138, the light reflected from the front surface may not have any significant contribution to the interference pattern detected at the camera 108. 〇 See Figure 7, - Equal path interferometers are available for other instrumentation platforms, such as interference microscopes. The interference microscope Π0 includes a main 胄172 and a movable interferometer objective 174. The host 172 includes a light source, 146 and a lens and field light assembly 176 (which includes a lens 173, a field aperture 175, and an illumination aperture stop m) to collimate light from the source "" The filter, the expansion, and the guide are directed toward an illumination beam splitter 178. Beam splitter m: Light is directed toward the interference objective 174. The beam splitter 178 also receives the light 'back from the interfering object' and directs the returned light to a camera 108 through the image aperture plate (10) and a barrel lens. 19 201100751 and an I: The objective lens 174 includes an objective lens 184, an interferometer beam splitter 116, and a plurality of pieces 104. To view (or measure) a particular surface of the object 102, a mechanical sweeping mechanism 186 produces an old read (four) 174 ν 186 / mouth direction 188 scan interference objective 乂 adjust & splitter 116_ surface 122 The distance from the object ι〇2 被 that is being viewed. The movable interferometer mirror 174 can replace the Millau, McKinson, or Linnick type of interference objective used in the system. The mouth is a microscope; 170# $ ^ is used - a road-controlled interferometer, which is useful for sweeping cat white light. Dry up, Brother 174 can be smaller than the McKesson or Linnick type of mirror. Referring to Fig. 8, in an r« binary mode, the 'Essence 1 190 for an equal path interferometer includes a reference component 1 9 2 and a +' 牛虑v 〒兀忏 and interferometer splitting 1 94. The orientation of the spectroscope 194 with respect to the orientation of the vertical optical axis 1Q6 is inclined by an angle > the orientation of the test piece 192 with respect to the vertical optical axis (10) is inclined by an angle ^ In this configuration, the " reference beam 1 96 totals from the reference component 】 92 = surface 200 reflected twice and from the interference beam splitter surface 2 〇 2, twice. The reference beam 196 travels back and forth between the pR surface 2〇2 of the beam splitter 194 and the R surface 200 of the reference element M2 twice before the reference beam 196 is combined with the measurement aperture 198. The thickness T1 of the reference element 192 is a half of the thickness τ2 of the beam splitter 194' such that the reference beam 196 and the measuring beam 198 pass an equal number of apertures. The distance between the PR surface 2〇2 of the beam splitter 194 and the front surface 137 of the object 1〇2 to be measured may be approximately the pR surface 2〇2 of the beam splitter 194 and the surface 192 (four) surface 20 of the optical element 194. The distance between them is twice. Similar to the example in the figure, the optical assembly 190 can be used with an instrument mainframe, or 20 201100751, which can be used in an interference microscope. An advantage of the optical assembly is that Compared to the example of Figure 1-4, which provides an increase in the working distance between the beam splitter 194 and the test object 102, s \,

In some embodiments, the interferometer beam splitter (eg, 116 or reference element (eg, 104 or 192) can be non-planar. For example, if the test object 102 is spherical, the pR reference of the reference element (eg, 1〇4 and 192) The surface (e.g., 118 or 200) may be a comparable spherical shape. 范例 y 显 显 叫 叫 叫 叫 叫 叫 叫 叫 叫 ΡΊ ΡΊ π π π 表面 表面 表面 范例 范例 范例 范例 范例 范例 范例 范例 范例 范例 范例 范例. Interferometer 22A includes a wedge shaped reference element 226 and a wedge shaped interferometer beam splitter 228. The beam splitter has a PR surface 232 and an AR surface 242. The reference element 226 has a μ surface 230 and an AR surface 24A, wherein the (9) surface 230 and surface 224 of the test object 222 are asymmetric with respect to the pR surface 232 of the beam splitter 228. The PR surface 232 separates an incoming beam 244 into a measuring beam and a reference beam 236' that travel an equal path length before the PR surface 232 combines to form an overlapping beam 238. The interference pattern of the overlapping beams 238 can be analyzed to provide information as to whether, for example, the surface 224 of the test object 222 matches or deviates from the desired surface profile represented by the PR surface 230 of the reference element 226. The interferometer 1GG + 'imaging module or system for capturing or recording the interference pattern (including the imaging lens 136 and the camera 1 〇 8) has a certain depth of focus, so that objects outside the depth of focus become out of focus due to the camera The images captured by 1〇8 appear blurred. In some embodiments, the interferometer can be configured to have certain components outside of the depth of focus of the imaging system to relax the requirements for component quality. For example, if the glass substrate is outside the depth of focus of the feedstock, the 瑕_ of the glass substrate is out of focus and has little or negligible effect on the interference pattern captured by the photographers (10). This allows the use of lower cost components to reduce the overall cost of the system while still maintaining high efficiency. Referring to the drawings, in some embodiments, in addition to the interferometer 25A including a reference element 252 that is flipped over the reference element 1〇4 of the interferometer 1〇〇, the interferometer 250 has an analog-like interferometer_ The reference element 252 has an anti-reflection coating 12 on the surface of the face alignment half 114 and has a portion of the reflective coating 11 8 on the surface facing the interferometer beam splitter 116. The 60 input light hits the AR coating 120 before it hits the pR coating 丨 18. This configuration may have the advantage that there are no glazing elements in the depth of focus of the imaging system of the interferometer 25 。. In this example The depth of focus is defined by the wavelength of the light divided by the square of the numerical aperture. For example, at a wavelength of 50 〇 nm, the focal depth of an imaging system with a numerical aperture of 〇.〇〇5 is 20 mm. The imaging system is designed to project A pattern of interference between light reflected from the PR surface 118 of the reference element 252 and light reflected from the surface of the object 12 or the surface in the object 120, so the focus is located at the pr surface 118 of the reference element 252. And the surface of the object 12 being measured. When the beam splitter 116 and the reference element 丨〇4 are positioned to separate beyond the focus (in this example, 20 mm), the splitter substrate becomes out of focus. This can be seen for the quality of the glass substrate used in the interferometer 250. Requirement, particularly at high spatial frequencies. Referring to Figure 11, in some embodiments, an interferometer 26 has a 22 201100751 configuration 'which is similar to the interferometer 250 (Figure i〇), and components, The pr surface two 262, which has (m) and has - additional light, is positioned to be partially or completely compensated for by the reference element 252 and the pre-study of the surface of the beam splitter 116: the phase difference between the beams (2), Caused by the difference between the light beam 2 126 and the measured light, the material encountered by the first beam 126 and m, for example, in the interferometer 250 of FIG. 10, although the beams 126 and 128 are the same distance, the measuring beam 128 ratio The reference beam 126 passes through more glass. As another example, if the thickness of the reference element 252 is not the same as the thickness of the interferometer beam splitter 116, even if the first beam travels the same distance, the beam 1 26 & 1 28 may have a phase difference. Extra Optical elements (e.g., color compensator 262) may partially or completely compensate for the phase difference between beams 126. Additional optical elements may be placed outside the depth of focus of the imaging system to relax the quality of the additional optical components. In the example of FIG. u, the dispersion compensator 262 is placed closer to the beam splitter 116 than the reference element 118 such that the dispersion compensator 262 is outside the depth of focus of the imaging system (the focus center is located at the reference element 252) PR surface 118). Referring to Figure 12A, in some embodiments, an interferometer includes an optical assembly 270 that alternatively uses reflections from the front or back surface of the interferometer beam splitter to produce a three-beam interference pattern A measuring beam and two reference beams provide a substantially equal path through the glass. The optical assembly 27A includes a reference component 252 and an interferometer beam splitter 272. The reference element 252 has an anti-reflection surface R1 and a portion of the reflective surface (having a reflectance of about 5 〇 0 / 〇). The beam splitter 272 has two partially reflective surfaces (5) and R4 (each having a reflectivity of approximately 12% from 201100751). The surfaces R1, R2, R3 and R4 are sequentially positioned. The example in Figure 12A is illustrated, which does not tilt the reference element and the beam splitter to eliminate unwanted reflections, and has non-parallel input and output beams to make the beam path easier to see. The first portion of the light is transmitted through the surfaces R1 and R2' and reflected at the surface R3 to form a first reference beam A278. The first reference beam 278 is partially reflected from surface R2 and returns to surface R4 at which point reference beam A278 is partially reflected in the _ path, which is approximately collimated and coextensive with the original illumination, but travels in the opposite direction . Referring to Figure 12B, the second portion of the light is transmitted through the surfaces Ri," and R3' and is reflected at surface R4 to form a second reference beam B28. The second reference beam 280 is partially reflected from surface R2 and returned to the surface. The reference beam is partially reflected at the point in the path, which is approximately collimated and coextensive with the original illumination, but travels in the opposite direction. The third part of the light is transmitted through the surface H R3 & R4. The measuring beam M282 is measured at the surface to be combined with the first reference beam A278, and the surface R3 is combined with the second reference beam β28(). The overlapping beams travel toward the camera 108, and the detection is in the - Interference between reference beam 278, second reference beam Β28, and measurement beam Μ 282. A method of determining the reflectance of surfaces R2, R3, and R4 to achieve a south (e.g., maximum) contrast of the beam interference pattern is described below. There is no stray reflection now, the interference intensity of the single-image point is: Ι-\Εα·, Εβ+Ε^ (1) B280 In this heart, the heart is the reference beam Α278, the reference beam 24 201100751 and the measuring light The complex electric field amplitude of M282. The complex reflectances of the surface r 1 . . . R4 are denoted as ri·..4', respectively, and the transmittances of these surfaces are denoted as h.. 4. Trace the reference beams A and β through System, for the input field 厶 get

Ea = EB = Entxt2tWlr, t2txeh (3) 〇 In this 9 series, there is a phase shift of the optical path difference (0PD) between the two reference beams Α and Β. Equations (2) and (3) are reduced to two Ea - E0t't2t3r2r3r4 (4) (5) Assume that the beam splitter surface R2; ? and R3 are perfectly parallel, the phase associated with the optical path difference φ = 〇 and - moxibustion To constructive interference with a reference beam, we can write an equivalent reference beam field as 〇Er = 2£' measurement field (6)

Em = E0t2xt22tltlrMem (7) The intensity I 祜 zinc in the equation (1), one, is reduced to a beam equivalent i = \er+em\2 (8) leads to the familiar intensity formula I = IR + IM+ 24hhi c〇s ( 0) (9) 25 (10) 201100751 Here (Π) h = at^:t^r2r,r, 4=3⁄43⁄43⁄4

R

(12) (13) RM=h\2 (14) Reference beam net intensity N2 is the reference reflection (A) or (4 of the intensity of e), which means to achieve good fringe contrast The rate does not need to be high γ _ h +Im to define the stripe contrast as (15) the largest stripe in the middle of the comparison K = 1 for / 7 祜 忐. m β ~ pole transport. Use equation (10) (11) When τ sinks τ times rm, the 'maximum contrast can be achieved. It is reduced to (16) t: rm = ar2r3r4 U7). As a specific example, the object 12G is the "bare glass surface, ^ has 4% reflection, 50% of the reference surface (R2) reflectivity, and for μ and only the same reflectivity, and the dielectric film, the material R1 achieves 〇% of the back shoulder 26 (18) 201100751 rate. In this example, -^1=0 ^2 ~ 50% and 4 = do Ru = 4% for the stripe contrast p = 丨(19) 2^4-(1-/?4)2 4% = 〇 it has Solution and 4 = 12.4%. Ancient κ; rate profit. For example, an object can be reflected by a higher spectrometer to provide maximum contrast reflectance. For the calculation of 30% of objects, it has been assumed that in addition to the measuring beam and the two reference beams A and B, the ancient Ganxian And his reflection reaches the instrument imaging system. Similar to the example of Figure 10, the reference elements in the optical assembly 27〇 can be tilted first to reduce or eliminate unwanted reflections and result in a flat input and output beam. Referring to Fig. 13, a tenth, 丄Ο = type optical assembly 220 includes a plane flattened eight-leaf knife precursor 272 tilted by an angle α and a tilted approximately equal to 2 (the reference element angle of the angle of χ. In this example, the unwanted single-surface reflection from surface...4 is not returned parallel to the output beam path. There are still unplanned beams from surface R4 that are reflected from the surface and again from surface R4 to the output beam. There are also unplanned beams from surface R3 that are reflected from surface R2 and again from the surface to the wheel. When the illumination is low spatial and temporally coherent, these beams do not have the correct path length to interfere; They only "view light is added to the image and does not otherwise disturb the required interference pattern. The net effect can be 27 201100751 to reduce the relative stripe contrast by, for example, 2 〇%. Referring to Figure 14, in some embodiments, via modification The interferometer 1 provides an interferometer 300 instead of using a collimator 3〇2 outside the imaging path. There is no collimator in this critical path to directly image the object 20. Camera i 〇 8. The field lens can be positioned between, for example, light source 110 and illumination beam splitter 112. Because field lens 302 is not involved in the imaging of object 120-test element 104, field lens 3〇2 need not be the same as the collimator The quality, while still allowing the interferometer to obtain accurate measurements. The field lens 21. Can be, for example, a diffraction or Fresnel lens. In the example shown in Figure 1, in order to measure the surface of a large object 120 = Sexuality may require the use of a large collimator i 14 to provide a sufficiently large light field. Large diameter, high quality collimators may be expensive. In the crucible shown in Figure 14, a large aperture field mirror is used. That is, it is obviously more cost-effective than a large-diameter device and can be substantially cost-effective when manufacturing an interferometer. The interferometer shown in Figures 4, 10 and U can also be modified to use a field-generation collimator. The V interferometer can be used to measure the flatness of the discs of many types of objects, such as glass discs used in hard discs, and the disc 2 has a front and rear reflective surface. The interferometer uses a light source. Has low spatial coherence, allowing reflection from the back reflection surface There is a negligible contribution to the measurement light reflected by the ::: surface and the interference pattern reflected from the reference surface. The interferometer can also be used to measure other types of disc media surfaces. Other features, features and advantages It is within the scope of the present invention. 28 201100751 Rugao®it' can provide a pedestal to support (iv) the test object (10). The pedestal can be adjustable and configured to position the test object 1G2 to define the optical path of the measuring beam 8. The length, which is substantially equal to the optical path length of the reference beam. The orientation of the wedge-shaped reference element 21 of Figure 2 can be rotated rapidly so that the PR surface of the reference τ piece faces the interferometer beam splitter. The configuration of the reference elements and interferometer beamsplitters in the 140 and the interference objective 174 of FIG. 7 may be replaced by other configurations, such as those shown in Figures 8, 9, 10, U, 〇 12A, 12B, and 13. The tilt angle of the reference element and the interferometer beam splitter can be different from the above. The reference elements and the partial anti-surfaces of the interferometer beamsplitter can be formed at respective internal interfaces within the optical elements and need not necessarily be the outer surfaces as shown in Figures 1-4 and 7-14. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram of an exemplary interferometer for measuring the surface of an object. 2 and 3 are diagrams of an exemplary optical assembly arranged with a path length equal to Ο for the reference beam and the measurement beam. Figure 4 is a diagram of an example interferometer for phase shifting interferometry. Figures 5 and 6 are diagrams. Figure 7 is a diagram of an exemplary equal path interferometer for interference microscopy. Figure 8 is a diagram of an example optical assembly. Figure 9 is a diagram of an exemplary optical assembly for measuring a non-planar surface. Figures 10 and 11 are diagrams of an exemplary interferometer for measuring the surface of an object. Example 0 29 201100751 Example Optical Assembly Figure 1 2A and 1 2B are diagrams that can be used in an interferometer.

The pattern. figure. [Description of main component symbols] 100, 220, 250, 260, 300: interferometer. 102, 222: test object; 2 5 2 : reference component; 104, 118, 192, 210, 226, 106: optical axis; 108: Camera; 110, 160: light source; 11 2: illumination beam splitter; 114: collimator; 116, 178, 194, 212, 228, 272: beam splitter; 120: object; 124, 214, 216, 240, 242: AR surface; 122, 200, 202, 218, 220, 230, 232: PR surface; 126, 196, 236: reference beam; 128, 198, 234: measuring beam; 130, 180: aperture stop; 136: imaging lens 1 3 7 : front surface; 138 : rear surface; 201100751 140 : interferometer sub-assembly; 142 : instrument main unit; 144 : equal path interferometer; 146 : low coherent light source; 148 : phase shifter; 149 : accessory installation Disk; 15 0: interference signal; 162: first peak; 164: second peak; 170: interference microscope; 172: host; 173: lens; 174: interference objective; 175: field diaphragm; 176: lens and field light阑 assembly; 177: illumination aperture stop; 184: objective lens; 186 ·• mechanical scanning mechanism; 190, 220, 270: total optical 210; 302: field lens; 224: surface; 238: overlapping beam; 244: beam; 262: dispersion compensator. 31

Claims (1)

201100751 VII. Patent application scope: 1. An optical assembly for use in an interferometer, the optical assembly comprising: first and second partial reflective surfaces, positioned along the optical axis and oriented to different illegal lines to the optical axis An angle, wherein the 'second partial reflective surface is configured to: 〇 receive light transmitted through the first partial reflective surface along the optical path; 11) transmit a portion of the received light to the test object to define the measurement light of the interferometer; and y Ui The other portion of the received light is directed toward the first partial reflective surface: a reference light defining the interferometer, wherein the reference light travels at least once back and forth between the second and first partially reflective surfaces. 2. The optical assembly of claim i, wherein the illegal line: the reference light passes through the first and second partial reflective surfaces at least once before the second partial reflective surface reflects the reference light back along the optical axis . 3: The optical assembly of claim 2, wherein the illegal line tweeting reference light is a partially reflective surface of the vertical human contact during the passage thereof. VIII. The optical assembly of claim 1, wherein the illegal line angle of the H-knife reflecting surface is twice that of the second part. The illegal line angle of the knives on the surface of the knives is as follows. For example, the optical oil component of the third paragraph of the patent application is as follows: the first part - one-half times.非法 非法 32 32 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 After the first portion reflects the surface) and the reference light (after the reference light is made at least once back and forth between the second body and the first partial reflective surface). 7. The optical assembly of claim 1, comprising: a first light 70, having a first partially reflective surface; and a second optical element having a first partial reflective surface. 8. The optical assembly of claim 7, wherein the first and second optical elements each have another surface having an anti-reflective coating. 9. The optical assembly of claim 7, wherein the first blade reflective surface is spaced apart from the second partially reflective surface by an distance greater than an imaging module that captures an interference pattern between the reference light and the measurement light. Depth of focus. 10. The optical assembly of claim 9, wherein the optical component of the interferometer is positioned such that the reference light does not pass through the glass within the depth of focus of the imaging module. The optical assembly of claim 7, wherein the first optical element has another surface having an anti-reflection coating. 12. The optical assembly of claim 5, wherein the first optical element is oriented such that the first partially reflective surface faces the second partially reflective surface of the second optical element and the anti-reflective coating of the first optical element Back to the first partial reflective surface. The optical assembly of claim 12, wherein the distance between the first partial reflective surface and the second partially reflective surface is greater than an imaging module for capturing an interference pattern between the reference light and the measurement light. Depth of focus. 33 201100751 14. The optical assembly of claim 13, further comprising: a dispersion compensator positioned between the first optical element and the second optical element to compensate for phase between the measured light and the reference light Poor, the dispersion compensator is positioned near the third optical element and is outside the depth of focus of the imaging module. 15. The optical assembly of claim 11, wherein the first optical element is oriented 'such that the first partially reflective surface faces away from the second partially reflective surface of the second optical element' and the anti-reflective coating of the first optical element Facing the first part of the reflective surface. 16. The optical assembly of claim 3, further comprising: a second partial reflective surface. 17. The optical assembly of claim 16, wherein the third partially reflective surface is configured to: I) receive light transmitted through the first partially reflective surface along the optical axis; II) transmit a portion of the received light to Testing the object to define the measurement light. and, iU) reflecting another portion of the received light back toward the first partial reflection surface to the interferometer & i ^ yiyi - the second reference light, wherein the second reference is first in the second And a path that travels at least once back and forth between the first partially reflective surfaces. 18. The optical assembly of claim 7, wherein the portion of the reflective surface is on the outer surface of the optical element. 19. The optical assembly of claim 7, wherein the eight reflective surfaces are formed at respective inner interfaces within the optical component. 2: > The optical assembly of claim 1 of the patent scope further includes: a collimation of 'receiving light from the light source and projecting the collimated light to the first portion of the surface. 21 _ The optical assembly of claim 1, further comprising: a mirror that receives light from the light source and projects the light onto the first partially reflective surface, after the reference light is reflected by the first partially reflective surface and the reference light is detected Prior to detector detection, the field lens is positioned outside of the imaging path through which the reference light travels. The optical assembly of claim 3, wherein the first portion of the reflective surface has a reflectance ranging from about 1% to about 3%. 23. The optical assembly of claim 1, wherein the second portion of the reflective surface has a reflectance ranging from about 4% to about 6%. 24. An interference system comprising: an optical assembly as claimed in claim 1; and a dry beta instrument base comprising a light source and a detector; wherein the 'light source is configured to produce transmission through the first partial reflection table and Light received by the first partially reflective surface, and wherein the detector is configured to receive information including the measured light and the combined light and providing a spatial distribution of the combined light. 25_ If the application (4) Fan (4) 24 items of the interference system, wherein the instrument base further comprises an aperture stop, the position is blocked from the light of the interferometer ^, which contacts the first part of the reflective earth surface along the optical axis and Reflected from the surface of the eighth-eighth reflection back to the interferometer base. 〇 26. The interferometric system of claim 24, wherein the oscillating base further comprises an aperture apex, a dry, " light that contacts the first portion along the optical axis to reflect w, The pedestal reflective surface is reflected back to the interferometer base. (4) - Part 35 201100751 = Intervention system of the 24th patent scope, including the seat ' to support the test object. The bottom of the interference system, such as _ the patent scope of the 27th, the i is clamped to measure the optical path length of the optical-seat light of the light. The length is substantially equal to the interference system phase of the reference abdomen as in claim 24, to vary the difference in the length of the path between the measurement light and the reference path. For example, the interferometric system of claim 29 mechanically couples the interferometer meimei g Z, the phase shifting 仪's pedestal to the optical assembly and is configured to change the keys 成=成和(4) between objects The distance, in order to change the optical path of the measuring light t, is an interference system according to item 24 of the patent scope, wherein the source of the light source is used to provide low-coherence interferometry. Please refer to the dry (four) system of the 24th item of the patent scope, and its goods 'frequency laser light source. It is an interference system according to item 24 of the patent scope 2, wherein the broadband mode of the light source and the laser mode adjustment of the high homology interference. For example, the interferometric system of claim 33, in which the light source is a laser diode, 兀 营 ^ μ ” * 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以 以And operating in a laser mode when the current is higher than its laser threshold. The interferometric system of claim 1 wherein the first-shot surface comprises a non-planar surface. 36 201100751 36 two-interference method, including: f optical axis clamps the first and second partial reflection surface; relative to the light vehicle will be the first month flute w illegal line angle; and the second part of the reflective surface is oriented to different _ The direction of the optical axis of the flat pupil transmits the light to the second partial reflection surface through the first partial reflection surface; and the second partial reflection surface transmits the first portion of the light to the test object to measure the light, and Reflecting the second portion of the light toward the first partially reflective surface to define the reference light; and, the first portion of the reflective surface 'reflecting a portion of the second portion of the light toward the surface of the reflective surface' such that the reference light is in the second The first portion of the reflective surface travels at least once back and forth. In the method of claim 36, the oriented first and second partial reflective surfaces comprise illegal linear angles that direct the first and second partial reflective surfaces to different t So that the reference light passes between the first and second partially reflective surfaces at least once before the second partial reflective surface reflects the reference dot 5 4» 沿 back along the optical axis of the optical axis. 38. The method of directing the first and second partial reflective surfaces includes directing the first and second partially reflective surfaces to different illegal line angles such that the reference light contacts the one of the reference lights at a normal incidence therebetween Partially reflective surface. 39. The method of claim 36, comprising: at the second force surface, '. Measure the ray (after it is reflected from the test object back to the second part. And reference light (after at least one of it travels back and forth between the second 37 201100751 and the first partially reflective surface). 40. As claimed in claim 39, At the end of the page, the information on the spatial distribution of the knots is provided. 41 · The method of applying the patent range % item ^ fS , m ^ ^ , includes providing an aperture 阑, blocking to stay away from the second The direction of the partial surface is reflected from the first portion of the reflective surface. The method of claim 36, comprising positioning the test object having a reflective surface to define an optical path length equal to the reference light on the light body of the measurement light. Length, large 43. The method of the patent scope 帛 42, including changing the difference between the optical path length between the measuring light and the reference light. 44. The method of claim (2), including changing the optical assembly And measuring the distance between the objects to change the optical path length of the measurement light, the optical assembly including the first and second partially reflective surfaces. And the method of claim 36, further comprising directing the optical element having the third portion of the surface to the outer surface of the optical member such that the outer surface of the optical element having the first partial reflective surface faces the second Partially reflective surface. 46. The method of claim (10), wherein the reference light is transmitted from the first partially reflective surface to the second partially reflective surface without passing through any of the glass elements. 47. The method of applying for the ninth item of the patent scope includes positioning the second part of the reflective surface at a distance from the reflective surface of the first-eighth and the main two music, which is greater than the detection in the measurement light and the table p卩站斗_ 园安^上, 〆号光的干β图案的影像模块焦38 201100751 深。 48. The method of claim 47, comprising passing the reference light through a dispersion compensator 'which compensates for a difference in phase between the measurement light and the reference light due to a difference in optical path length between the reference light and the measurement light. And positioning the dispersion compensator outside of the depth of focus of the imaging module. 49. The method of claim 5, further comprising: locating a third reflective surface along the optical axis; 〇 orienting the third partially reflective surface parallel to the second partially reflective surface; “reflecting the surface at the second portion, Transmitting a second portion of the light transmitted by the first partially reflective surface to the test object to define the measurement light and reflecting the P-knife of the light back toward the first partially reflective surface to define a second reference light; and ^ at the σ 卩 77 reflective surface And reflecting a portion of the fourth portion of the light toward the two-part reflective surface such that the second reference light travels at least once back and forth between the second and first reflective surfaces. Wherein, transmitting the light = passing the first-part reflective surface comprises passing the collimation (four) through the first-part surface. A method of claim 36, wherein the method of reflecting the first part is axe It will then pass through a mirror and after the reference light is reflected by the first part 矣&^ to detect the reflection surface of the μ knife and the reference light is detected by the detector ] The field lens was previously positioned outside of the imaging path through which the reference light travels.